Increased risk of disease, disability, and death are well-known hazards of old age. While disease incidence and death are the conventional indices of a society’s health status, functional disability is perhaps the most consequential index when dealing with health in old age. This chapter defines the character and magnitude of disability in old age, reviews preventive and therapeutic approaches to specific and general causes of disability among the elderly, and examines the role of healthcare organizations in facilitating the delivery of such services.
DIMENSIONS OF THE PROBLEM
Concept and Measurement of Disability
Conceptually, disability has been classified by the World Health Organization as part of a continuum of stages of disease impact that include:1,2
Impairment. The loss or abnormality of psychological, physiological, or anatomical integrity at the level of specific organ systems.
Disability/Activity Limitation. The inability to perform an activity within the range considered normal for a human being, hence a functional limitation experienced at the level of the person as a whole.
Handicap/Participation Restriction. A disadvantage resulting from an impairment or disability which if not addressed, limits an individual’s ability to participate in society.
Collectively this continuum has been referred to as the “disablement model.” While each stage of the model has specific assessment tools and interventions, which are discussed throughout this chapter, the key overarching principles in the intervention for all three stages are holistic patient-centered evaluation, multidisciplinary coordination, and longitudinal care.
A wide variety of systems have been developed for measuring functional ability/disability.3 The best known of these are the Activities of Daily Living (ADL) and the Instrumental Activities of Daily Living (IADL) indices. The ADL index, first introduced by Katz and colleagues, classifies limitations in six fundamental, sociobiological functions of daily living: bathing, dressing, toileting, transferring from bed or chair, continence, and feeding.4 Lawton and others broadened the scope with the IADL concept which incorporates measures of more complex adaptive or self-maintaining functions: cooking, medication management, telephone use, transportation, housekeeping, money management, and grocery shopping.5 In addition to screening and care planning for individual patients, these measurement systems have been very useful for describing the disability status of the elderly population, estimating community and institutional service needs, and evaluating outcomes of interventions designed to limit disability.
The concept of “preclinical disability” focuses on identifying stages in the natural history of functional loss, which precede the onset of overt ADL or IADL dependencies. This phenomenon was originally measured in terms of adaptive modifications in the performance of common tasks such as doing housework or getting out of bed.6 Physiologic and performance measures of lower extremity function have also been shown to be powerful predictors of future onset of frank disability across diverse older populations.7
In the last 30 years, there has been an increased ...